High-activity isomerization catalyst and process

ABSTRACT

A catalyst and process is disclosed to selectively upgrade a paraffinic feedstock to obtain an isoparaffin-rich product for blending into gasoline. The catalyst comprises a support of a sulfated oxide or hydroxide of a Group IVB (IUPAC 4) metal, a first component of at least one lanthanide element or yttrium component, which is preferably ytterbium, and at least one platinum-group metal component which is preferably platinum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of application Ser. No. 10/717,812 filedNov. 20, 2003 now U.S. Pat. No. 6,881,873, which is a Division ofapplication Ser. No. 09/942,237, now U.S. Pat. No. 6,706,659, thecontents of which are hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This work was performed under the support of the U.S. Department ofCommerce, National Institute of Standards and Technology, AdvancedTechnology Program, Cooperative Agreement Number 70NANB9H3035. TheUnited States Government has certain rights in this invention.

FIELD OF THE INVENTION

This invention relates to an improved catalytic composite and processfor the conversion of hydrocarbons, and more specifically for theselective upgrading of a paraffinic feedstock by isomerization.

BACKGROUND OF THE INVENTION

The widespread removal of lead antiknock additive from gasoline and therising fuel-quality demands of high-performance internal-combustionengines have compelled petroleum refiners to install new and modifiedprocesses for increased “octane,” or knock resistance, in the gasolinepool. Refiners have relied on a variety of options to upgrade thegasoline pool, including higher-severity catalytic reforming, higher FCC(fluid catalytic cracking) gasoline octane, isomerization of lightnaphtha and the use of oxygenated compounds. Such key options asincreased reforming severity and higher FCC gasoline octane result in ahigher aromatics content of the gasoline pool at the expense oflow-octane heavy paraffins.

Refiners are also faced with supplying reformulated gasoline to meettightened automotive emission standards. Reformulated gasoline differsfrom the traditional product in having a lower vapor pressure, lowerfinal boiling point, increased content of oxygenates, and lower contentof olefins, benzene and aromatics. Benzene content generally is beingrestricted to 1% or lower, and is limited to 0.8% in U.S. reformulatedgasoline. Gasoline aromatics content is likely to be lowered,particularly as distillation end points (usually characterized as the90% distillation temperature) are lowered, since the high-boilingportion of the gasoline which thereby would be eliminated usually is anaromatics concentrate. Since aromatics have been the principal source ofincreased gasoline octanes during the recent lead-reduction program,severe restriction of the benzene/aromatics content and high-boilingportion will present refiners with processing problems. These problemshave been addressed through such technology as isomerization of lightnaphtha to increase its octane number, isomerization of butanes asalkylation feedstock, and generation of additional light olefins asfeedstock for alkylation and production of oxygenates using FCC anddehydrogenation. This issue often has been addressed by raising the cutpoint between light and heavy naphtha, increasing the relative quantityof naphtha to an isomerization unit. The performance of light-naphthaisomerization catalysts thus is increasingly important in refineryeconomics.

U.S. Pat. No. 2,939,896 B1 teaches isomerization of paraffinichydrocarbons using a catalyst containing platinum, halogen and a sulfateof aluminum, magnesium and/or zirconium deposited on activated alumina.The patent does not disclose additional metal components of thecatalyst, however. U.S. Pat. No. 5,036,035 B1 teaches a catalyst, andits use in isomerization, containing sulfated zirconium oxide orhydroxide and a platinum-group metal. The patent teaches that reductionof the platinum-group metal is not favorable.

U.S. Pat. No. 4,918,041 B1, U.S. Pat. No. 4,956,519 B1 and EuropeanPatent Application 0 666 109 A1 disclose a sulfated catalyst, and itsuse in isomerization, comprising an oxide or hydroxide of Group III orGroup IV; oxide or hydroxide of Groups V, VI or VII; and oxide orhydroxide of Group VIII; '109 also discloses a component from a list ofGroup VIII metals and metal combinations.

U.S. Pat. No. 3,915,845 B1 discloses a catalyst and its use comprising aplatinum-group metal, Group IVA metal, halogen and lanthanide in anatomic ratio to platinum-group metal of 0.1 to 1.25. U.S. Pat. No.5,493,067 B1 teaches that isoparaffins and olefins are alkylated bycontact with a solid superacid such as sulfated zirconia optionallycontaining added metals and containing added heteropolyacids orpolyoxoanions.

U.S. Pat. No. 5,310,868 B1 and U.S. Pat. No. 5,214,017 B1 teach catalystcompositions containing sulfated and calcined mixtures of (1) a supportcontaining an oxide or hydroxide of a Group IV-A element, (2) an oxideor hydroxide of a Group VI, VII, or VIII metal, (3) an oxide orhydroxide of a Group I-B, II-B, III-A, III-B, IV-A, V-A metal, and (4) ametal of the lanthanide series.

U.S. Pat. No. 5,212,136 B1 discloses a solid super acid catalyst usefulin alkylation processes comprising sulfated and calcined mixtures of asupport of an oxide or hydroxide of a Group IV-A element, an oxide orhydroxide of molybdenum, and an oxide or hydroxide of a Group I-B, II-B,III-A, III-B, IV-B, V-A or VI-A metal other than molybdenum or a metalof the lanthanide series.

SUMMARY OF THE INVENTION

A purpose of the present invention is to provide an improved catalystand process for hydrocarbon conversion reactions. Another purpose of thepresent invention is to provide improved technology to upgrade naphthato gasoline. A more specific purpose is to provide an improved catalystand process for the isomerization of light naphtha to obtain ahigh-octane gasoline component. This invention is based on the discoverythat a catalyst containing ytterbium and platinum components providessuperior performance and stability in the isomerization of light naphthato increase its isoparaffin content.

A broad embodiment of the present invention is directed to a catalystcomprising a sulfated support of an oxide or hydroxide of a Group IVB(IUPAC 4) metal, preferably zirconium oxide or hydroxide, at least afirst component which is a lanthanide element or yttrium component, andat least a second component being a platinum-group metal component. Thefirst component preferably consists of a single lanthanide-serieselement or yttrium and the second component preferably consists of asingle platinum-group metal. Preferably, the first component isytterbium and the second component is platinum. The catalyst optionallycontains an inorganic-oxide binder, especially alumina.

An additional embodiment of the invention is a method of preparing thecatalyst of the invention by sulfating the Group IVB metal oxide orhydroxide, incorporating a first component, a lanthanide element,yttrium, or any mixture thereof, and the second component, aplatinum-group metal, and preferably binding the catalyst with arefractory inorganic oxide.

In another aspect, the invention comprises converting hydrocarbons usingthe catalyst of the invention. In yet another embodiment, the inventioncomprises the isomerization of isomerizable hydrocarbons using thecatalyst of the invention. The hydrocarbons preferably comprise lightnaphtha which is isomerized to increase its isoparaffin content andoctane number as a gasoline blending stock.

These as well as other embodiments will become apparent from thedetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plot of the percent conversion of pentane versus theionic radius for 8 coordination of a series of catalysts where the firstcomponent of the catalysts was varied.

FIG. 2 shows a plot of the cyclohexane conversation versus temperatureof a series of catalysts. Catalysts of the present invention arecompared to reference catalysts.

DETAILED DESCRIPTION OF THE INVENTION

The support material of the catalyst of the present invention comprisesan oxide or hydroxide of a Group IVB (IUPAC 4) metal, see Cotton andWilkinson, Advanced Inorganic Chemistry, John Wiley & Sons (FifthEdition, 1988). Preferably, the metal is selected from zirconium andtitanium, with zirconium being especially preferred. The preferredzirconium oxide or hydroxide is converted via calcination to crystallineform. Sulfate is composited on the support material to form, it isbelieved without so limiting the invention, a mixture of Brönsted andLewis acid sites. A component of a lanthanide-series element isincorporated into the composite by any suitable means. A platinum-groupmetal component is added to the catalytic composite by any means knownin the art to effect the catalyst of the invention, e.g., byimpregnation. Optionally, the catalyst is bound with a refractoryinorganic oxide. The support, sulfate, metal components and optionalbinder may be composited in any order effective to prepare a catalystuseful for the isomerization of hydrocarbons.

Production of the support of the present catalyst may be based on ahydroxide of a Group IVB (IUPAC 4) metal as raw material. For example,suitable zirconium hydroxide is available from MEI of Flemington, N.J.Alternatively, the hydroxide may be prepared by hydrolyzing metaloxy-anion compounds, for example ZrOCl₂, ZrO(NO₃)₂, ZrO(OH)NO₃, ZrOSO₄,TiOCl₂ and the like. Note that commercial ZrO(OH)₂ contains asignificant amount of HF, about 1 weight percent. Zirconium alkoxidessuch as zirconyl acetate and zirconium propoxide may be used as well.The hydrolysis can be effected using a hydrolyzing agent such asammonium hydroxide, sodium hydroxide, potassium hydroxide, sodiumsulfate, (NH₄)₂HPO₄ and other such compounds known in the art. The metaloxy-anion component may in turn be prepared from available materials,for example, by treating ZrOCo₃ with nitric acid. The hydroxide aspurchased or generated by hydrolysis preferably is dried at atemperature of from about 100 to 300° C. to vaporize volatile compounds.

A sulfated support is prepared by treatment with a suitable sulfatingagent to form a solid strong acid. Liquid acids whose strength isgreater than sulfuric acid have been termed “superacids”. A number ofliquid superacids are known in the literature including substitutedprotic acids, e.g., trifluoromethyl substituted H₂SO₄, triflic acid andprotic acids activated by Lewis acids (HF plus BF₃). While determinationof the acid strength of liquid superacids is relatively straightforward,the exact acid strength of a solid strong acid is difficult to directlymeasure with any precision because of the less defined nature of thesurface state of solids relative to the fully solvated molecules foundin liquids. Accordingly, there is no generally applicable correlationbetween liquid superacids and solid strong acids such that if a liquidsuper acid is found to catalyze a reaction, there is no correspondingsolid strong acid which one can automatically choose to carry out thesame reaction. Therefore, as will be used in this specification, “solidstrong acids” are those that have an acid strength greater than sulfonicacid resins such as Amberlyst®-15. Additionally, since there isdisagreement in the literature whether some of these solid acids are“superacids” only the term solid strong acid as defined above will beused herein. Another way to define a solid strong acid is a solidcomprising of interacting protic and Lewis acid sites. Thus, solidstrong acids can be a combination of a Bronsted (protonic) acid and aLewis acid component. In other cases, the Bronsted and Lewis acidcomponents are not readily identified or present as distinct species,yet they meet the above criteria.

Sulfate ion is incorporated into a catalytic composite, for example, bytreatment with sulfuric acid in a concentration usually of about0.01-10N and preferably from about 0.1-5N. Compounds such as hydrogensulfide, mercaptans or sulfur dioxide, which are capable of formingsulfate ions upon calcining, may be employed as alternative sources.Preferably, ammonium sulfate is employed to provide sulfate ions andform a solid strong acid catalyst. The sulfur content of the finishedcatalyst generally is in the range of about 0.5 to 5 mass-%, andpreferably is from about 1 to 2.5 mass-%. The sulfated composite isdried, preferably followed by calcination at a temperature of about 500to 700° C. particularly if the sulfation is to be followed byincorporation of the platinum-group metal.

A first component, comprising one or more of the lanthanide-serieselements, yttrium, or mixtures thereof, is another essential componentof the present catalyst. Included in the lanthanide series arelanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium and lutetium. Preferred lanthanide series elements includelutetium, ytterbium, thulium, erbium, holmium, terbium, and mixturesthereof Ytterbium is a most preferred component of the present catalyst,and it is especially preferred that the first component consistsessentially of a ytterbium component. The first component may in generalbe present in the catalytic composite in any catalytically availableform such as the elemental metal, a compound such as the oxide,hydroxide, halide, oxyhalide, carbonate or nitrate or in chemicalcombination with one or more of the other ingredients of the catalyst.The first component is preferably an oxide, an intermetallic withplatinum, a sulfate, or in the zirconium lattice. The materials aregenerally calcined between 600 and 800° C. and thus in the oxide form.Although it is not intended to so restrict the present invention, it isbelieved that best results are obtained when the first component ispresent in the composite in a form wherein substantially all of thelanthanide or yttrium component is in an oxidation state above that ofthe elemental state such as in the form of the oxide, oxyhalide orhalide or in a mixture thereof and the subsequently described oxidationand reduction steps that are preferably used in the preparation of theinstant catalytic composite are specifically designed to achieve thisend. The lanthanide element or yttrium component can be incorporatedinto the catalyst in any amount which is catalytically effective,suitably from about 0.01 to about 10 mass-% lanthanide or yttrium, ormixtures, in the catalyst on an elemental basis. Best results usuallyare achieved with about 0.5 to about 5 mass-% lanthanide or yttrium,calculated on an elemental basis. The preferred atomic ratio oflanthanide or yttrium to platinum-group metal for this catalyst is atleast about 1:1, preferably about 2:1 or greater, and especially about5:1 or greater.

The first component is incorporated in the catalytic composite in anysuitable manner known to the art, such as by coprecipitation,coextrusion with the porous carrier material, or impregnation of theporous carrier material either before, after, or simultaneously withsulfate though not necessarily with equivalent results. For ease ofoperation, it is preferred to simultaneously incorporate the lanthanideelement or yttrium with the sulfate. It is most preferred to incorporatethe platinum-group metal component last. As to the lanthanide serieselement or yttrium and the platinum-group metal, the order between thetwo does not have a significant impact.

One method of depositing the first component involves impregnating thesupport with a solution (preferably aqueous) of a decomposable compoundof the lanthanide element or elements or yttrium. By decomposable ismeant that upon heating, the lanthanide element or yttrium compound isconverted to the lanthanide element or yttrium element or oxide with therelease of byproducts. Illustrative of the decomposable compounds of thelanthanide elements are suitable lanthanide complexes or compounds suchas, nitrates, halides, sulfates, acetates, organic alkyls, hydroxides,and the like compounds. The first component can be impregnated into thecarrier either prior to, simultaneously with, or after theplatinum-group metal component, although not necessarily with equivalentresults.

A second component, a platinum-group metal, is an essential ingredientof the catalyst. The second component comprises at least one ofplatinum, palladium, ruthenium, rhodium, iridium, or osmium; platinum ispreferred, and it is especially preferred that the platinum-group metalconsists essentially of platinum. The platinum-group metal component mayexist within the final catalytic composite as a compound such as anoxide, sulfide, halide, oxyhalide, etc., in chemical combination withone or more of the other ingredients of the composite or as the metal.Amounts in the range of from about 0.01 to about 2-wt. % platinum-groupmetal component, on an elemental basis, are preferred. Best results areobtained when substantially all of the platinum-group metal is presentin the elemental state.

The second component, a platinum-group metal component, is deposited onthe composite using the same means as for the first component describedabove. Illustrative of the decomposable compounds of the platinum groupmetals are chloroplatinic acid, ammonium chloroplatinate, bromoplatinicacid, dinitrodiamino platinum, sodium tetranitroplatinate, rhodiumtrichoride, hexa-amminerhodium chloride, rhodium carbonylchloride,sodium hexanitrorhodate, chloropalladic acid, palladium chloride,palladium nitrate, diamminepalladium hydroxide, tetraamminepalladiumchloride, hexachloroiridate (IV) acid, hexachloroiridate (III) acid,ammonium hexachloroiridate (III), ammonium aquohexachloroiridate (IV),ruthenium tetrachloride, hexachlororuthenate, hexa-amminerutheniumchloride, osmium trichloride and ammonium osmium chloride. The secondcomponent, a platinum-group component, is deposited on the supporteither before, after, or simultaneously with sulfate and/or the firstcomponent though not necessarily with equivalent results. It ispreferred that the platinum-group component is deposited on the supporteither after or simultaneously with sulfate and/or the first component.

In addition to the first and second components above, the catalyst mayoptionally further include a third component of iron, cobalt, nickel,rhenium or mixtures thereof. Iron is preferred, and the iron may bepresent in amounts ranging from about 0.1 to about 5-wt. % on anelemental basis. The third component, such as iron, may function tolower the amount of the first component, such as ytterbium, needed inthe optimal formulation. The third component may be deposited on thecomposite using the same means as for the first and second components asdescribed above. When the third component is iron, suitable compoundswould include iron nitrate, iron halides, iron sulfate and any othersoluble iron compound.

The catalytic composite described above can be used as a powder or canbe formed into any desired shapes such as pills, cakes, extrudates,powders, granules, spheres, etc., and they may be utilized in anyparticular size. The composite is formed into the particular shape bymeans well known in the art. In making the various shapes, it may bedesirable to mix the composite with a binder. However, it must beemphasized that the catalyst may be made and successfully used without abinder. The binder, when employed, usually comprises from about 0.1 to50 mass-%, preferably from about 5 to 20 mass-%, of the finishedcatalyst. The art teaches that any refractory inorganic oxide binder issuitable. One or more of silica, alumina, silica-alumina, magnesia andmixtures thereof are suitable binder materials of the present invention.A preferred binder material is alumina, with eta- and/or especiallygamma-alumina being favored. Examples of binders which can be usedinclude but are not limited to alumina, silica, silica-alumina andmixtures thereof. Usually the composite and optional binder are mixedalong with a peptizing agent such as HCl, HNO₃, KOH, etc. to form ahomogeneous mixture which is formed into a desired shape by formingmeans well known in the art. These forming means include extrusion,spray drying, oil dropping, marumarizing, conical screw mixing, etc.Extrusion means include screw extruders and extrusion presses. Theforming means will determine how much water, if any, is added to themixture. Thus, if extrusion is used, then the mixture should be in theform of a dough, whereas if spray drying or oil dropping is used, thenenough water needs to be present in order to form a slurry. Theseparticles are calcined at a temperature of about 260° C. to about 650°C. for a period of about 0.5 to about 2 hours.

The catalytic composites of the present invention either as synthesizedor after calcination can be used as catalysts in hydrocarbon conversionprocesses. Calcination is required to form zirconium oxide fromzirconium hydroxide. Hydrocarbon conversion processes are well known inthe art and include cracking, hydrocracking, alkylation of botharomatics and isoparaffins, isomerization, polymerization, reforming,dewaxing, hydrogenation, dehydrogenation, transalkylation, dealkylation,hydration, dehydration, hydrotreating, hydrodenitrogenation,hydrodesulfirization, methanation, ring opening, and syngas shiftprocesses. Specific reaction conditions and the types of feeds, whichcan be used in these processes, are set forth in U.S. Pat. Nos.4,310,440 B1 and 4,440,871 B1 which are incorporated by reference. Apreferred hydrocarbon conversion process is the isomerization ofparaffins.

In a paraffin isomerization process, common naphtha feedstocks boilingwithin the gasoline range contain paraffins, naphthenes, and aromatics,and may comprise small amounts of olefins. Feedstocks which may beutilized include straight-run naphthas, natural gasoline, syntheticnaphthas, thermal gasoline, catalytically cracked gasoline, partiallyreformed naphthas or raffinates from extraction of aromatics. Thefeedstock essentially is encompassed by the range of a full-rangenaphtha, or within the boiling point range of 0° to 230° C. Usually thefeedstock is light naphtha having an initial boiling point of about 10°to 65° C. and a final boiling point from about 75° to 110° C.;preferably, the final boiling point is less than about 95° C.

The principal components of the preferred feedstock are alkanes andcycloalkanes having from 4 to 7 carbon atoms per molecule (C₄ to C₇),especially C₅ to C₆, and smaller amounts of aromatic and olefinichydrocarbons also may be present. Usually, the concentration of C₇ andheavier components is less than about 20 mass-% of the feedstock.Although there are no specific limits to the total content in thefeedstock of cyclic hydrocarbons, the feedstock generally containsbetween about 2 and 40 mass-% of cyclics comprising naphthenes andaromatics. The aromatics contained in the naphtha feedstock, althoughgenerally amounting to less than the alkanes and cycloalkanes, maycomprise from 2 to 20 mass-% and more usually from 5 to 10 mass-% of thetotal. Benzene usually comprises the principal aromatics constituent ofthe preferred feedstock, optionally along with smaller amounts oftoluene and higher-boiling aromatics within the boiling ranges describedabove.

Contacting within the isomerization zones may be effected using thecatalyst in a fixed-bed system, a moving-bed system, a fluidized-bedsystem, or in a batch-type operation. A fixed-bed system is preferred.The reactants may be contacted with the bed of catalyst particles ineither upward, downward, or radial-flow fashion. The reactants may be inthe liquid phase, a mixed liquid-vapor phase, or a vapor phase whencontacted with the catalyst particles, with excellent results beingobtained by application of the present invention to a primarilyliquid-phase operation. The isomerization zone may be in a singlereactor or in two or more separate reactors with suitable means therebetween to ensure that the desired isomerization temperature ismaintained at the entrance to each zone. Two or more reactors insequence are preferred to enable improved isomerization through controlof individual reactor temperatures and for partial catalyst replacementwithout a process shutdown.

Isomerization conditions in the isomerization zone include reactortemperatures usually ranging from about 40° to 250° C. Lower reactiontemperatures are generally preferred in order to favor equilibriummixtures having the highest concentration of high-octane highly branchedisoalkanes and to minimize cracking of the feed to lighter hydrocarbons.Temperatures in the range of about 100° to about 200° C. are preferredin the process of the present invention. Reactor operating pressuresgenerally range from about 100 kPa to 10 MPa absolute, preferablybetween about 0.3 and 4 MPa. Liquid hourly space velocities range fromabout 0.2 to about 25 hr⁻¹, with a range of about 0.5 to 15 hr⁻¹ beingpreferred.

Hydrogen is admixed with or remains with the paraffinic feedstock to theisomerization zone to provide a mole ratio of hydrogen to hydrocarbonfeed of from about 0.01 to 20, preferably from about 0.05 to 5. Thehydrogen may be supplied totally from outside the process orsupplemented by hydrogen recycled to the feed after separation from thereactor effluent. Light hydrocarbons and small amounts of inerts such asnitrogen and argon may be present in the hydrogen. Water should beremoved from hydrogen supplied from outside the process, preferably byan adsorption system as is known in the art. In a preferred embodiment,the hydrogen to hydrocarbon mol ratio in the reactor effluent is equalto or less than 0.05, generally obviating the need to recycle hydrogenfrom the reactor effluent to the feed.

Upon contact with the catalyst, at least a portion of the paraffinicfeedstock is converted to desired, higher octane, isoparaffin products.The catalyst of the present invention provides the advantages of highactivity and improved stability. When the first component is selected tobe ytterbium, the catalyst of the present invention has the additionaladvantage of increased ring opening activity.

The isomerization zone generally also contains a separation section,optimally comprising one or more fractional distillation columns havingassociated appurtenances and separating lighter components from anisoparaffin-rich product. Optionally, a fractionator may separate anisoparaffin concentrate from a cyclics concentrate with the latter beingrecycled to a ring-cleavage zone.

Preferably part or all of the isoparaffin-rich product and/or theisoparaffin concentrate are blended into finished gasoline along withother gasoline components from refinery processing including, but notlimited to, one or more of butanes, butenes, pentanes, naphtha,catalytic reformate, isomerate, alkylate, polymer, aromatic extract,heavy aromatics, gasoline from catalytic cracking, hydrocracking,thermal cracking, thermal reforming, steam pyrolysis and coking,oxygenates such as methanol, ethanol, propanol, isopropanol, tert-butylalcohol, sec-butyl alcohol, methyl tertiary butyl ether, ethyl tertiarybutyl ether, methyl tertiary amyl ether and higher alcohols and ethers,and small amounts of additives to promote gasoline stability anduniformity, avoid corrosion and weather problems, maintain a cleanengine and improve driveability.

The following examples serve to illustrate certain specific embodimentsof the present invention. These examples should not, however, beconstrued as limiting the scope of the invention as set forth in theclaims. There are many possible other variations, as those of ordinaryskill in the art will recognize, which are within the scope of theinvention.

EXAMPLE 1

Catalyst samples of Table 1 were prepared starting with zirconiumhydroxide that had been prepared by precipitating zirconyl nitrate withammonium hydroxide at 65° C. The zirconium hydroxide was dried at 120°C., ground to 40-60 mesh. Multiple discrete portions of the zirconiumhydroxide were prepared. Solutions of either ammonium sulfate or a metalsalt (component 1) were prepared and added to the portions of zirconiumhydroxide. The materials were agitated briefly and then dried with80-100° C. air while rotating. The impregnated samples were then driedin a muffle oven at 150° C. for two hours under air. Solutions of eitherammonium sulfate or a metal salt (component 2, where component 2 is notthe same as component 1) were prepared and added to the dried materials.The samples were briefly agitated and dried while rotating. The sampleswere then calcined at 600-700° C. for 5 hours. The final impregnationsolutions of chloroplatinic acid were prepared and added to the solids.The samples were agitated and dried while rotating as before. Thesamples were finally calcined at 525° C. in air for 2 hours. In Table 1below, “A” indicates that catalysts were made at modifier levels of 1wt. %, 2 wt. %, 3 wt. % and 4 wt. %; “B” indicates that catalysts weremade at sulfate levels of 6 wt. %, 7 wt. %, and 8 wt. %; and “C”indicates that catalysts were made at platinum levels of 0.25 wt. %, 0.5wt. %, 0.75 wt. %, and 1 wt. %.

TABLE 1 Modifier Modifier Level Fe Pt SO₄ Ce A 0 0.4 7 Dy A 0 0.4 7 Er A0 0.4 7 Eu A 0 0.4 7 Gd A 0 0.4 7 Ho A 0 0.4 7 La A 0 0.4 7 Lu A 0 0.4 7Nd A 0 0.4 7 Pr A 0 0.4 7 Sm A 0 0.4 7 Tb A 0 0.4 7 Tm A 0 0.4 7 Y A 00.4 7 Yb 0.3 0 0.3 7 Yb 0.4 0 0.4 7 Yb 0.5 0 0.5 7 Yb 1 0 0.4 7 Yb 1 0 CB Yb 1.8 0 C B Yb 2 0 0.4 7 Yb 2.7 0 C B Yb 3 0  0.375 7 Yb 3 0 0.4 7 Yb3.5 0 C B Yb 4 0 0.4 7 Ce 1 1 0.4 7 Ce 1 1.5 0.4 7 Yb 1 1.5 0.4 7 Yb 1 20.4 7

EXAMPLE 2

Catalysts were prepared as described in Example 1 containing 2 wt. %modifier, 0.4-wt. % platinum, and 7-wt. % sulfate. Approximately 95 mgof each sample was loaded into a multi-unit reactor assay. The catalystswere pretreated in air at 450° C. for 2-6 hours and reduced at 200° C.in H₂ for 0.5-2 hours. 8 wt. % pentane in hydrogen was then passed overthe samples at 150° C., approximately 1 atm, and 2.5 hr⁻¹ WHSV (based onpentane only). The products were analyzed using online gaschromatographs and the results are shown in FIG. 1, note that areplicate of the ytterbium-containing catalyst was tested. FIG. 1 is aplot of percent pentane conversion vs. the ionic radii for 8coordination of the lanthanide series or yttrium materials used tomodify a platinum sulfated zirconia catalyst. The ionic radii weredetermined by reference to Huheey, J. E. Inorganic Chemistry—Principlesof Structure and Reactivity, 2nd Ed.; Harper & Row: New York, 1978. Theplot shows a maximum conversion around 112 picometers (ytterbium). Theactivity drops off rapidly as the ionic radius increases aboveapproximately 115 picometers.

EXAMPLE 3

Catalysts were prepared as described in Example 1, with the firstcatalyst (Catalyst 1 in FIG. 2) containing 3 wt. % ytterbium, about0.375 to about 0.4 wt. % platinum, and 7 wt. % sulfate; the secondcatalyst (Catalyst 2 in FIG. 2) containing 1 wt. % ytterbium, about0.375 to about 0.4 wt % platinum, 1 wt. % iron, and 6 wt. % sulfate, andthe third catalyst (Catalyst 3 in FIG. 2) containing 0.5 wt. %manganese, 1 wt. % iron, about 0.375 to about 0.4 wt % platinum and 7wt. % sulfate. Additionally, two reference catalysts were obtained, thefirst reference catalyst containing platinum on sulfated zirconia(Catalyst 4 in FIG. 2), and the second reference catalyst containingplatinum, iron, and manganese on sulfated zirconia (Catalyst 5 in FIG.2). Approximately 10.5 g of each sample was loaded into a multi-unitreactor assay. The catalysts were pretreated in air at 450° C. for 2-6hours and reduced at 200° C. in H2 for 0.5-2 hours. Hydrogen and a feedstream containing 36 wt. % n-pentane, 52 wt. % n-hexane, 10 wt. %cyclohexane and 2 wt. % n-heptane was passed over the catalysts at 135°C., 150° C., 163° C., and 176° C., at approximately 450 psig, and 2 hr⁻¹WHSV. The hydrogen to hydrocarbon molar ratio was 1.3. The products wereanalyzed using online gas chromatographs and the percent conversion ofcyclohexane was determined at the different temperatures. The resultsare shown in FIG. 2 which shows that significant ring opening capabilitywas demonstrated by the platinum and ytterbium on sulfated zirconiacatalyst.

1. A process for the isomerization of a paraffinic feedstock to obtain aproduct having an increased isoparaffin content comprising contactingthe paraffinic feedstock in an isomerization zone maintained atisomerization conditions comprising a temperature of from 40 to 250° C.,pressure of from 100 kPa to 10 MPa and liquid hourly space velocity offrom 0.2 to 25 hr⁻¹ with a solid acid isomerization catalyst, comprisinga sulfated support comprising on oxide or hydroxide of elements of GroupIVB (IUPAC4) of the Periodic Table, a first component selected from thegroup consisting of at least one lanthanide-series element, mixturesthereof, and yttrium, and a second component selected from the groupconsisting of platinum-group metals and mixtures thereof, wherein theatomic ratio of the first component to the second component is at leastabout 2, and recovering an isoparaffin-enriched product.
 2. The processof claim 1 wherein free hydrogen is present in the isomerization zone inan amount from about 0.01 to about 20 moles per mole of C₅+ hydrocarbonspresent in the isomerization zone.
 3. The process of claim 1 wherein theisomerization conditions comprise a temperature from about 100 to about200° C., a pressure from about 300 kPa to about 4 MPa, and a liquidhourly space velocity of from 0.5 to 15 hr⁻¹, and wherein free hydrogenis present in the isomerization zone in an amount from about 0.05 to 5moles per mole of C₅+ hydrocarbons present in the isomerization zone. 4.The process of claim 1 wherein the isomerization catalyst furthercomprises a refractory inorganic-oxide binder.
 5. The process of claim 1wherein the catalyst further comprises from about 2 to about 50 mass-%of a refractory inorganic-oxide binder.
 6. The process of claim 5wherein the refractory inorganic-oxide binder comprises alumina.
 7. Theprocess of claim 1 wherein the first component is selected from thegroup consisting of ytterbium, lutetium, thulium, or mixtures thereofand the second component is platinum.
 8. The process of claim 1 whereinthe catalyst further comprises a third component selected from the groupconsisting of iron, cobalt, nickel, rhenium, and mixtures thereof. 9.The process of claim 8 wherein the third component is iron in an amountfrom about 1 to about 5 wt. %.
 10. A process for the isomerization of aparaffinic feedstock to obtain a product having an increased isoparaffincontent comprising contacting the paraffinic feedstock in anisomerization zone maintained at isomerization conditions comprising atemperature of from 40 to 250° C., pressure of from 100 kPa to 10 MPaand liquid hourly space velocity of from 0.2 to 25 hr⁻¹ with a solidacid isomerization catalyst, comprising a sulfated support comprising anoxide or hydroxide of elements of Group IVB (IUPAC 4) of the PeriodicTable, a first component selected from the group consisting of at leastone lanthanide-series element, mixtures thereof, and yttrium, and asecond component selected from the group consisting of platinum-groupmetals and mixtures thereof, recovering an isoparaffin-enriched product,and using at least a portion of the isoparaffin-enriched product toblend a gasoline product.
 11. The process of claim 10 wherein freehydrogen is present in the isomerization zone in an amount from about0.01 to about 20 moles per mole of C₅+ hydrocarbons present in theisomerization zone.
 12. The process of claim 10 wherein theisomerization conditions comprise a temperature from about 100 to about200° C., a pressure from about 300 kPa to about 4 MPa, and a liquidhourly space velocity of from 0.5 to 15 hr⁻¹, and wherein free hydrogenis present in the isomerization zone in an amount from about 0.05 to 5moles per mole of C₅+ hydrocarbons present in the isomerization zone.13. The process of claim 10 wherein the isomerization catalyst furthercomprises a refractory inorganic-oxide binder.
 14. The process of claim13 wherein the refractory inorganic-oxide binder comprises alumina. 15.The process of claim 10 wherein the isomerization catalyst furthercomprises from about 2 to about 50 mass-% of a refractoryinorganic-oxide binder.
 16. The process of claim 10 wherein the atomicratio of the first component to the second component is at least about2.
 17. The process of claim 10 wherein the first component is selectedfrom the group consisting of ytterbium, lutetium, thulium, or mixturesthereof and the second component is platinum.
 18. The process of claim10 wherein the catalyst further comprises a third component selectedfrom the group consisting of iron, cobalt, nickel, rhenium, and mixturesthereof.
 19. The process of claim 18 wherein the third component is ironin an amount from about 1 to about 5 wt. %.